Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1999-12-28
2001-09-11
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S373000, C428S374000
Reexamination Certificate
active
06287689
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the fields of synthetic filaments and fabrics made therefrom. More particularly, it concerns synthetic filaments that have both low surface energy and high strength.
2. Description of Related Art
Fabrics which are water-repellent (i.e. provide a barrier to moisture) while allowing the passage of water vapor and other gases are desirable for use in apparel, shoes, tents and camping equipment, packaging, medical apparel, and medical supplies. Such fabrics require fibers that have both a low surface energy to repel water and a strength high enough to be processible into a useful fabric. Other desirable fabrics are both water-repellent and do not allow the passage of water vapor and other gases, for use in airtight packaging and medical supplies.
In packaging, protective apparel, and industrial filtration, a need exists for fabrics that are stable to both heat and chemicals. Such fabrics require fibers both low in surface energy and high enough in strength to be processible into a useful fabric, as well as heat and chemical resistance.
One class of water-repellent fabrics are those made by applying a finish to a fabric or its component filaments before or after the weaving or knitting process. The finish is intended to provide the low surface energy needed to repel water. However, such finishes tend to have poor durability and washfastness.
A second class of water-repellent fabrics are those comprising water-repellent materials. An example of this class is a fabric comprising polytetrafluoroethylene (PTFE) sold by W. L. Gore Inc. under the trade name GORE-TEX®. Known uses of PTFE fabrics are limited to lamination of the PTFE fabric to a textile fabric. This suggests that PTFE fabrics, although having low surface energy, do not have high enough strength to be useful fabrics per se.
Therefore, it is desirable to have a textile fabric made of filaments that exhibit low surface energy and strength high enough to be processible into useful fabrics. It is also desirable for such filaments to be produced by high throughput, economical spinning technology. Although filaments with a core/sheath structure wherein the sheath comprises a halogenated polymer are known (Chimura et al., U.S. Pat. Nos. 3,930,103 and 3,993,834), the core of the known filaments comprises primarily methyl methacrylate, and is not useful in forming moisture-resistant fabrics. Although core/sheath filaments wherein the core comprises nylon and the sheath comprises a grafted olefinic polymer are known, such as Tabor et al., U.S. Pat. No. 5,372,885, no such filaments are known to comprise a sheath useful in heat- and chemical-resistant fabrics.
SUMMARY OF THE INVENTION
In one embodiment, the present invention relates to a filament comprising a first longitudinally extending component formed of at least one filament-forming polymer, and a second longitudinally extending component formed of at least one polymer, wherein the second longitudinally extending component is in contact with the surface of the first longitudinally extending component, and wherein the filament has a contact angle greater than or equal to 90 degrees and a tenacity of at least 2.0 g/den. In one embodiment, the first longitudinally extending component forms the core of the filament, and the second longitudinally extending component is in the form of a sheath that surrounds the circumference of the core. In another embodiment, the second longitudinally extending component is in the form of one or more stripes located on the surface of the first longitudinally extending component.
In another embodiment, the present invention also relates to a yarn, wherein the yarns comprise a plurality of filaments as described above. The present invention also relates to a fabric comprising a plurality of said yarns, wherein the spacing between the yarns is sufficiently small to provide a barrier to liquids and sufficiently large to allow the passage of gases, or is sufficiently small to provide a barrier to liquids and to gases.
In a further embodiment, the present invention relates to a method for making a yarn comprising coextruding (1) a first molten stock comprising at least one filament-forming polymer, and (2) a second molten stock comprising at least one polymer, whereby the second molten stock forms a second longitudinally-extending component on the surface of the first molten stock, thereby forming molten filaments, and quenching the molten filaments, a plurality of which are formed into yarn. The method can further comprise drawing the yarn.
In yet another embodiment, the present invention also relates to a method of making a fabric, comprising providing a plurality of yarns, wherein each said yarn comprises a plurality of filaments as described above, and weaving or knitting the plurality of yarns with a spacing between the yarns sufficiently small to provide a barrier to liquids and sufficiently large to allow the passage of gases, to yield the fabric. Alternatively, the spacing is sufficiently small to provide a barrier to liquids and a barrier to gases.
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“Surface Energetics of Nylon 66 Fibers”, Martha L. Tate, Yashavanth K. Kamath, Sheldon P. Wesson, and Sigrid B. Ruetsch, Art.
Elliott John J.
Fisher W. Keith
Hancock J. Gregory
Horn David B.
Edwards N.
Howrey Simon Arnold & White , LLP
Solutia Inc.
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